1. Field of the Invention
The present invention relates to a device for maintaining the normal spacing between two vertebrae defining, in the vertebral column, the ends of a cavity resulting from the elimination of at least a part of a vertebra.
In a certain number of cases it proves necessary to ablate a vertebra, at least partially, in a patient. In fact, the fracture of a vertebra by shattering, particularly in the dorso-lumbar region, may cause compression of the spinal cord resulting in serious neurological troubles which may cause paraplegia. Similarly, a vertebral tumour whatever its level, may cause similar neurological problems. In both cases, recourse is had to removing the damaged vertebra, which must of course be replaced by a prosthesis. In the first case, a bone graft (internal prosthesis) is used which will be revascularized in a period of time between 6 and 9 months; in the second case, it is preferred to use a prosthesis made from a synthetic material, such for example as a resin.
2. Description of the Prior Art
It is known to use, as vertebral prosthesis frame, a buttress formed of a threaded rod both ends of which are housed in holes drilled in the vertebrae defining, in the spinal column, the ends of the cavity resulting from the removal, at least partial, of the vertebra. The threaded rod is held in these holes by nuts bearing on the end of vertebrae. The bone or synthetic prosthesis is then placed about this support.
A device of this type has however a certain number of disadvantages. On the one hand, such a buttress is relatively fragile considering the very high stresses to which it may be subjected. Furthermore, it is necessary to use a rod whose length is greater than the spacing between the end vertebrae, which causes difficulties in positioning.
The purpose of the present invention is therefore to overcome these drawbacks by proposing a vertebral prosthesis buttressing device whose height is adjustable, which facilitates positioning thereof, and which is designed so that it may withstand all the mechanical stresses to which it is likely to be subjected.